JPH0491682A - Supersonic motor - Google Patents

Abstract

PURPOSE:To prevent the abnormal abrasion between a rotor and a stator or the occurrence of noise even if high load is applied from outside to a driving system by setting the frictional force between a rotation member and a rotation output member smaller than the friction between a vibrator and the rotation member. CONSTITUTION:The frictional force of friction coupling between a rotor 6 and a rotation output member 7 is generated by a pressurizing spring 10, and the force is set to be smaller than the frictional force between a vibrating elastic body 1 and the rotor 6. That is, even if torque is given to the rotation output member 7 from outside, the rotor 6 never rotates since the frictional force to the stator is larger than the frictional force to the rotation output member 7, it follows that only the rotation output member 7 rotates. In case that high load is added to the rotation output member 7, the rotor 6 starts to slide to the rotation output member 7 before the rotation of the rotor 6 becomes unstable or the rotation stops, so the high load from the rotation output member 7 is never transmitted between the rotor 6.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultrasonic motor equipped with a friction clutch.

[Prior art] In recent years, by synthesis of vibrations, the surface particles of a vibrating elastic body have a circle,
Alternatively, an ultrasonic motor is provided that excites elliptical motion and relatively moves a member that makes frictional contact with the surface of the elastic body.

As ultrasonic motors, types formed in an annular shape and types formed in a rod shape have been proposed, but both of these have a vibrating elastic body that constitutes a stator to generate vibrations for driving. The basic driving principle is the same: bringing into frictional contact with a rotation converting member such as a rotor that converts drive vibrations formed in the vibrating elastic body into rotational force, and rotating the rotation converting member by the frictional force.

When an annular ultrasonic motor is used in a lens barrel, for example, as an autofocus drive source, it has the advantage of being able to directly apply the rotational output of the rotor to the focus lens without using a transmission mechanism such as a gear. However, an annular type ultrasonic motor has a disadvantage in terms of manufacturing cost compared to a rod-shaped type ultrasonic motor.

Unlike ring-shaped ultrasonic motors, rod-shaped ultrasonic motors cannot be arranged to surround a lens, for example, so the rotary force of the rotor is transmitted to a driven member, such as a focus lens, via a transmission mechanism such as a gear. The structure will be configured to convey information to the public.

[Problems to be Solved by the Invention] However, when a rod-shaped ultrasonic motor is used as a drive source and a driven member is driven via a transmission mechanism, a rotational output member such as a gear that transmits the rotational force of a rotor to the driven member is required. If the load is too high, the rotor rotation will become unstable, and in the worst case, the stator vibration will stop resonating and the rotor will stop rotating.
There have been problems in that the stator is vibrating but the rotor is still in place, causing noise (squealing) and abnormal wear between the stator and rotor.

Therefore, in order to solve such problems,
In No. 97281, the rotor is rotated idly when a high load is applied, but this method requires a new friction plate to be installed between the rotor and the output shaft, so it is not effective in terms of space and cost. I couldn't say that.

The present invention solves these conventional problems and provides a mechanism with a simple structure that can prevent abnormal wear between the rotor and stator and the generation of abnormal noise even when a high load is applied to the drive system from the outside. An object of the present invention is to provide an ultrasonic motor that can be obtained by using the same method as described above, and which can also be miniaturized.

[Means for Solving the Problems] The configuration of an ultrasonic motor that achieves the object of the present invention is based on an electric motor.
A rotating member is brought into frictional contact with a vibrator having a mechanical energy converting element via a pressure member, and an alternating current electric field is applied to the electro-mechanical energy converting element to excite drive vibration in the vibrator to generate a driving vibration in the rotating member. and a rotational output member that makes frictional contact with the rotational member to take out an output, and the frictional force between the rotational member and the rotational output member is greater than the frictional force between the vibrator and the rotational member. It is characterized by being set small.

[Function] In the ultrasonic motor configured as described above, when a high load is applied to the rotational output member, the rotational member starts to slide relative to the rotational output member before the rotation of the rotational member becomes unstable or stops.

[Example] The present invention will be described in detail below based on an example shown in the drawings.

FIG. 1 shows an embodiment of an ultrasonic motor according to the present invention,
FIG. 5(a) is a plan view, and FIG. 2(b) is a longitudinal cross-sectional view.

1 is a cylindrical vibrating elastic body made of a metal material, 2 is a presser body made of a metal material having an outer diameter of the same shape as the outer diameter of the vibrating elastic body 1, and 3a to 3d are the same diameter as the outer diameter of the vibrating elastic body 1. The annular piezoelectric element plates 48 to 4d are electrode plates of the piezoelectric element plates 3a to 3d. , piezoelectric element plate 3a~
3d, and by screwing bolts 2 through the presser body 2 and onto the vibrating elastic body 1, these are fixed together to constitute the stator of the ultrasonic motor A.

In the ultrasonic motor A, piezoelectric element plates 3a to 3d form mechanical vibrations in the stator by applying alternating current voltages with different phases from a power supply circuit (not shown) to electrode plates 4a to 4d of the stator. This combination excites a rope-like motion in the stator, and frictionally drives a rotor 6, which will be described later, which comes into frictional contact with the front end of the stator. A rotor 6 has a rear end portion (frictional contact portion) 6a in contact with a tapered portion 1a of the vibrating elastic body 1, and obtains an appropriate frictional force by pressurization by a pressure spring 10, which will be described later.

Reference numeral 7 denotes a rotation output member made of a frictionally stable material and having a gear 7a, which is frictionally coupled between the rear end surface and the end surface of the rotor 6. This gear 7a is for transmitting the rotation of the rotor 6 to the outside.

The friction force of the frictional connection between the rotor 6 and the rotational output member 7 is generated by the pressure spring 10, and the force is made smaller than the friction force between the vibrating elastic body 1 and the rotor 6 (so that the friction coefficient becomes smaller). ) is set.

That is, even if a rotational force is applied to the rotational output member 7 from the outside, the frictional force of the rotor 6 against the stator
It does not rotate because it is greater than the frictional force against (
, only the rotating a force member 7 will rotate.

On the other hand, a bearing 8 is provided on the inner diameter part of the rotation output member 7,
By fitting a hollow shaft 9 into the inner diameter portion of this bearing 8, the rotor 6 and rotation output member 7 are made rotatable.

The shaft 9 is fitted into the sliding portion 5a of the bolt 5 to align with the axis of the stator.

IO is a pressure spring, and by pressing the stepped portion 9a of the shaft 9, the flange portion 9b presses the bearing 8, and the pressing force causes the vibration elastic body 1 and the rotor 6, and the rotor 6 and the rotation output member 7 to The structure is such that a frictional force is generated between the two.

The pressurizing force of the pressurizing spring 10 is determined by inserting the hole 11c of the flat plate-shaped holding member 11 into the bottle part 5b formed at the tip of the bolt 5, and fixing it by a well-known method such as fixing with adhesive, for example. It is generated in

This ultrasonic motor A is fixed by screwing the holding member 11 to a fixing member (not shown) through screw holes 11a, 11b using screws (not shown).

In addition, when supporting the stator of an ultrasonic motor, it is necessary to avoid affecting the vibrations excited in the stator, and the end of the stator is at the antinode position of the vibration, and there is only displacement in the radial direction. Moreover, since the displacement is actually minute, it does not affect the vibration of the stator by fixing it with the pin portion 5b, which is one end of the stator.

In the ultrasonic motor configured in this way, when a high load is applied to the rotational output member 7, the rotation of the rotor 6 becomes unstable, or the rotor 6 starts to slide relative to the rotational output member 7 before it stops rotating. , a high load from the rotational output member 7 is not transmitted between the rotor 6 and the stator.

In order to achieve the above operation, the vibrating elastic body 1
The selection of materials for the rotor 6 and rotational output member 7 is a problem, but the vibration elastic body 1 is made of brass and the rotor 6 is made of aluminum, and the friction coefficient is set to 0.8 or more. When the above operation was performed using polyacetal and the coefficient of friction with the rotor 6 was 0.2 or less, it was confirmed that it worked well. It was confirmed that if there is, the rotor 6 and the rotational output member 7 will surely slip before the vibrating elastic body 1 and the rotor 6 slip.

As shown in the figure, the vibration elastic body 1, the rotor 6, and the rotation output member 7 are formed to have approximately the same diameter, and the holding member 11 is formed to have approximately the same diameter with respect to the vibration elastic body 1, the rotor 6, and the rotation output member 7. It is constructed so that it is larger than the diameter, and is assembled into a unit.

[Effects of the Invention] As described above, according to the present invention, even if a high load is applied to a rotational output member such as a gear, rotation of the rotational member such as a rotor becomes unstable or stops before it stops. Since the member starts to slide relative to the rotational output member, abnormal wear and abnormal noise between the vibrator and the rotating member can be prevented.

In addition, since the frictional drive for the rotating member is performed by the rotational output member itself, there is no need to install new parts, and it is inexpensive and does not require an increase in space. be.

In addition, since the components that make up the motor, including the friction mechanism, are assembled as one unit, unlike conventional methods, it is possible to use parts other than the motor, such as the transmission system for driving driven parts, as a countermeasure against high loads. There is no need to provide a mechanism, and the degree of freedom in application to various devices is dramatically increased, resulting in great effects.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of an ultrasonic motor according to the present invention,
FIG. 5(a) is a plan view, and FIG. 2(b) is a sectional view. 7: Rotation output member 9: Shaft 11: Holding member. 8: Bearing 10: Pressure spring load 4 A: 1: aa 5: Ultrasonic motor elastic vibrator ~ 3d: Piezoelectric element plate ~ 4d: Electrode plate bolt 6: Rotor 2: Presser body

Claims (3)

[Claims] 1. A rotating member is brought into frictional contact with a vibrator having an electro-mechanical energy conversion element via a pressure member, and an alternating current electric field is applied to the electro-mechanical energy conversion element to excite drive vibration in the vibrator to generate the energy. It includes a rotational output member that drives the rotational member and takes out an output by frictionally contacting the rotational member, and converts the frictional force between the rotational member and the rotational output member into the friction between the vibrator and the rotational member. An ultrasonic motor characterized by being set smaller than the force. 2. 2. The ultrasonic motor according to claim 1, wherein the frictional force between the rotating member and the rotational output member is generated by a pressure member that applies frictional force to the vibrator and the rotating member. 3. 3. The ultrasonic motor according to claim 1, wherein the vibrator, the rotating member, the rotating output member, and the pressure member are integrated into a unit.